Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$83.29	8.306%	$90.2081	$90.21	$90.20	$90.20
Purchase #2	$23.64	3.834%	$24.5464	$24.55	$24.55	$24.50
Purchase #3	$29.59	7.202%	$31.7211	$31.72	$31.70	$31.70
Purchase #4	$51.48	4.772%	$53.9366	$53.94	$53.95	$53.90
Purchase #5	$103.99	8.123%	$112.4371	$112.44	$112.45	$112.40
Purchase #6	$65.75	10.379%	$72.5742	$72.57	$72.55	$72.60
Purchase #7	$175.53	3.150%	$181.0592	$181.06	$181.05	$181.10
7 purchase totals =	$533.27		$566.4827	$566.49	$566.45	$566.40